Fantastik250 has that nailed. Although, you should look into the GTX 480. Its only about, say, $30 more than than a typical GTX 560. All you really need to make sure on though is that if you want to buy a GTX 480, you need a power supply that is at least 650 watts while being 80+ bronze and that your case would be able to hold that 10.5 inch beast.

Note: If you do end up buying the GTX 480, make sure it gets some damn good cooling; it can reach 90*C in demanding needs.